gh-129013: Don't expose async_generator_wrapped_value in PY_YIELD callbacks

Include/internal/pycore_genobject.h

@@ -67,6 +67,18 @@ extern PyObject *_PyAsyncGenValueWrapperNew(PyThreadState *state, PyObject *);
 extern PyTypeObject _PyCoroWrapper_Type;
 extern PyTypeObject _PyAsyncGenWrappedValue_Type;
 extern PyTypeObject _PyAsyncGenAThrow_Type;
+extern PyTypeObject _PyAsyncGenWrappedValue_Type;
+
+typedef struct _PyAsyncGenWrappedValue {
+    PyObject_HEAD
+    PyObject *agw_val;
+} _PyAsyncGenWrappedValue;
+
+#define _PyAsyncGenWrappedValue_CheckExact(o) \
+                    Py_IS_TYPE(o, &_PyAsyncGenWrappedValue_Type)
+#define _PyAsyncGenWrappedValue_CAST(op) \
+    (assert(_PyAsyncGenWrappedValue_CheckExact(op)), \
+     _Py_CAST(_PyAsyncGenWrappedValue*, (op)))
 
 #ifdef __cplusplus
 }

Lib/test/test_monitoring.py

@@ -2083,6 +2083,30 @@ def callback(code, instruction_offset):
         sys.monitoring.restart_events()
         sys.monitoring.set_events(0, 0)
 
+    @test.support.requires_working_socket()  # For asyncio
+    def test_yield_async_generator(self):
+        # gh-129013: Async generators have a special type that they
+        # use to yield values. This type shouldn't be exposed by PY_YIELD
+        # events.
+        asyncio = test.support.import_helper.import_module("asyncio")
+
+        async def gen():
+            yield 42
+
+        async def main():
+            async for _ in gen():
+                pass
+
+        def handle_yield(code, offset, value):
+            self.assertEqual(value, 42)
+
+        sys.monitoring.use_tool_id(0, "test")
+        sys.monitoring.register_callback(0, sys.monitoring.events.PY_YIELD, handle_yield)
+        sys.monitoring.set_events(0, sys.monitoring.events.PY_YIELD)
+
+        asyncio.run(main())
+        sys.monitoring.set_events(0, 0)
+
 
 class TestOptimizer(MonitoringTestBase, unittest.TestCase):
 
@@ -2329,3 +2353,6 @@ def test_enter_scope_two_events(self):
 
         finally:
             sys.monitoring.set_events(TEST_TOOL, 0)
+
+if __name__ == "__main__":
+    unittest.main()

Misc/NEWS.d/next/Core_and_Builtins/2025-01-19-14-15-36.gh-issue-129013.28rL6Z.rst

@@ -0,0 +1,2 @@
+Fix odd/unusable value when using :monitoring-event:`PY_YIELD` with an
+:term:`asynchronous generator`.

Objects/genobject.c

@@ -1441,19 +1441,6 @@ typedef struct PyAsyncGenAThrow {
 } PyAsyncGenAThrow;
 
 
-typedef struct _PyAsyncGenWrappedValue {
-    PyObject_HEAD
-    PyObject *agw_val;
-} _PyAsyncGenWrappedValue;
-
-
-#define _PyAsyncGenWrappedValue_CheckExact(o) \
-                    Py_IS_TYPE(o, &_PyAsyncGenWrappedValue_Type)
-#define _PyAsyncGenWrappedValue_CAST(op) \
-    (assert(_PyAsyncGenWrappedValue_CheckExact(op)), \
-     _Py_CAST(_PyAsyncGenWrappedValue*, (op)))
-
-
 static int
 async_gen_traverse(PyObject *self, visitproc visit, void *arg)
 {

Python/bytecodes.c

@@ -1312,9 +1312,16 @@ dummy_func(
         }
 
         tier1 op(_YIELD_VALUE_EVENT, (val -- val)) {
+            PyObject *yielded = PyStackRef_AsPyObjectBorrow(val);
+            if (_PyAsyncGenWrappedValue_CheckExact(yielded))
+            {
+                /* gh-129013: Async generators have a special wrapper that they
+                   yield. Don't expose that to the user. */
+                yielded = _PyAsyncGenWrappedValue_CAST(yielded)->agw_val;
+            }
             int err = _Py_call_instrumentation_arg(
                     tstate, PY_MONITORING_EVENT_PY_YIELD,
-                    frame, this_instr, PyStackRef_AsPyObjectBorrow(val));
+                    frame, this_instr, yielded);
             if (err) {
                 ERROR_NO_POP();
             }